package com.baugdev.encryptor.algo.aes;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class AESAlgorithm extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);
        
        Intent intent = this.getIntent() ;
        int actionType = intent.getIntExtra("ActionType",-1) ;
        String key = intent.getStringExtra("Key") ;
        String data = intent.getStringExtra("Data") ;
        
        Intent retIntent = new Intent() ;
        
        String result = null ;
        try {
        	if ( actionType == 1) {
        		result = decrypt(key, data) ;
			} else {
				result = encrypt(key, data) ;
			}
        } catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			//return data ;
			retIntent.putExtra("OutText", data) ;
			setResult(RESULT_CANCELED, retIntent) ;
        }
        retIntent.putExtra("OutText", result) ;
        setResult(RESULT_OK, retIntent) ;
        finish() ;
        //return result ;
    }
    
    /**
     * Usage:
     * <pre>
     * String crypto = SimpleCrypto.encrypt(masterpassword, cleartext)
     * ...
     * String cleartext = SimpleCrypto.decrypt(masterpassword, crypto)
     * </pre>
     * @author ferenc.hechler
     */
    
    public static String encrypt(String seed, String cleartext) throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] result = encrypt(rawKey, cleartext.getBytes());
		return toHex(result);
	}
	
	public static String decrypt(String seed, String encrypted) throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] enc = toByte(encrypted);
		byte[] result = decrypt(rawKey, enc);
		return new String(result);
	}

	private static byte[] getRawKey(byte[] seed) throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
		sr.setSeed(seed);
	    kgen.init(128, sr); // 192 and 256 bits may not be available
	    SecretKey skey = kgen.generateKey();
	    byte[] raw = skey.getEncoded();
	    return raw;
	}

	
	private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
	    byte[] encrypted = cipher.doFinal(clear);
		return encrypted;
	}

	private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
	    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
	    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
	    byte[] decrypted = cipher.doFinal(encrypted);
		return decrypted;
	}

	public static String toHex(String txt) {
		return toHex(txt.getBytes());
	}
	public static String fromHex(String hex) {
		return new String(toByte(hex));
	}
	
	public static byte[] toByte(String hexString) {
		int len = hexString.length()/2;
		byte[] result = new byte[len];
		for (int i = 0; i < len; i++)
			result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
		return result;
	}

	public static String toHex(byte[] buf) {
		if (buf == null)
			return "";
		StringBuffer result = new StringBuffer(2*buf.length);
		for (int i = 0; i < buf.length; i++) {
			appendHex(result, buf[i]);
		}
		return result.toString();
	}
	private final static String HEX = "0123456789ABCDEF";
	private static void appendHex(StringBuffer sb, byte b) {
		sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
	}
}